Sorry, I don´t have any exact answers to what you were looking for... but first of all, if you´re talking about real seafreight (not just “hitching a ride” on some smaller boat, for example), then I doubt airfreight is actually gonna cost you 4 times more than seafreight. Seafreight usually gets a lot cheaper than airfreight only, when your shipping distance is really long. Even then I doubt by sea would cost only 25% of what the same shipping would cost by air.

I haven´t shipped by sea to Chennai, but I have shipped by air out of Chennai in January 2008.... this is just my gut feeling, but destination charges at the seaport could bring a few surprises. And they do love their bureaucracy in India! Also when I was searching for options out of Chennai, I heard, that there had been some ´slow-down´ strikes at the seaport, and it meant nobody had a clue, if shipping by sea to Thailand would have taken two weeks, or six weeks. Even the quotes that I got were roughly the same by air and by sea – that actually made my decision very easy!

It is not exact science, but usually the shorter the distance, the clearer the benefits of using airfreight. Just generally seems to create less headache at both ends, although exceptions are always possible.

Too bad that there´s no ferry connection between India and Sri Lanka... (and was there not a plan to re-open such a service not a long time ago, wonder what happened to that)??